A long-term controlled trial of screening for hypertension in general practice.

A controlled trial was undertaken to evaluate the practical consequences of screening in general practice. Of 2420 people aged 40-64 years examined in 1967-68, 191 (7.9%) had previously been told, at some time, that they had raised blood-pressure, other than during pregnancy. However, only 77 (3-2%) had any record of current antihypertensive treatment. Screening resulted in a further 50 persons (2-1%) being newly diagnosed as hypertensive in 1967-68 and a further 9 in 1969-70. Antihypertensive treatment was given to 21 of these immediately following diagnosis, while the treatment was adjusted in 23 of those already known to be hypertensive. In 1972-73 the blood-pressures of the screening population were directly compared with the control group. No significant differences in the distributions of their blood-pressure levels were observed. Over 95% of the new hypertensives discovered by the screening process in the control group in 1972-73 had visited their general practitioners for some reason during the previous five years. This suggests that "case-finding" by general practitioners would be more cost-effective than setting up separate blood-pressure screening clinics. However, the results of this study indicate that we need to know more about how raised blood-pressure can be successfully controlled over a long time, before any mass screening programmes can be actively encouraged.